Electron discharge device



Aug. H8, w42. A. y. HAEFF 2,293,387

ELECTRON DISCHARGE DEVICE Original Filed Feb. 2, 1959 2 Sheets-Sheet 1 AT TORNEY.

Aug ES H942 A. v. HAEFF ELECTRON DISCHARGE DEVICE original Filed Feb. 2,1939 2 Sheets-Sheet 2 :g l IEIHHIBIH INVENTOR. ANDREW if. HAEFF A TTORNEY.

Patente-d ug. i8, 1942 UNM@ STATES PATENT OFFICE ELECTRON DISCHARGEDEVICE Andrew V. Haefi, East Grange, N'. lf., assigner to RadioCorporation of America, a corporation of Delaware 1s claim. (cl.25o-27.5)

My invention relates to electron discharge devices, particularly to suchdevices suitable for use at high frequencies.

The present application is a division of my application which issued asUnited States Patent 2,237,878 on April 8, 1941.

It is well known that conventional tubes become inoperative at very highfrequencies. The principal dimculties which prevent operation at highfrequencies are due chiefly to the following factors, that is, thefinite electron transit time producing abnormal loading of the inputcircuit and loss of transconductance of the tube, difficulty inobtaining necessary small coupling between the output electrode and theinput electrode which results in regeneration or excessive loading ofthe output circuit due to the reflected input losses and the consequentloss of power output and emciency, and increased losses in the circuitdue to the presence of large circulating currents at high frequenciesand due to an increase in eective resistance of the circuit.

The principal object of my invention is to provide an improved electrondischarge device particularly suitable for use at high frequencies.

More particularly it is an object of my invention to provide an electrondischarge device in which electron transit time is not criticallyrelated to the period of oscillation, which will function satisfactorilyat frequencies at which conventional tubes fail to operate, and in whichhigh frequency losses are minimized.

A further object of my invention is to 'provide an electron dischargedevice particularly suitable for use as an amplifier at very highfrequencies.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims, but theinvention itself will best be understood by reference to the followingdescription taken in connection with the accompanying drawings in whichFigures 1 to 4 inclusive are schematic diagrams i1- lustrating theprinciples of my invention, Figure 5 is a simplified diagrammaticrepresentation of an electron discharge device made according to myinvention, and Figures 6 to 11 inclusive are longitudinal sections ofelectron discharge devices made according to my invention, theassociated voltage sources being shown in Figures 6 and 7.

A better understanding of my invention can be had by discussing theprinciple involved. To illustrate the principle involved in electrondischarge devices made according to my invention reference is had toFigures 1 to 4 inclusive. 1n

Figure 1 is schematically shown the longitudinal 55 schematic section ofa quarter wave concentric line tank circuit comprising an inner tubularconductor 20 which may be cylindrical in cross section, and a hollowouter tubular conductor 2| concentric with the inner conductor 20 andelectrically connected to the inner conductor 20 by the conducting plate22. A second tubular conductor 2t which may be referred to as theaperture extension is coaxial with the conductor 29 and spaced axiallyfrom the conductor 20 to provide a gap 25. This tubular conductor g4 andthe outer conductor 2l are connected by the conducting plate 23. Thisarrangement provides a quarter wave concentric tank circuit. If anegatively charged body 26 is projected axially ythrough the innerconductor 28 from left to right, the conditions of the chargedistribution on the circuit as the body 26 is moved along the interiorof conductors 20 and 2d is indicated in' Figures 1 to inclusive. Asshown in the gures, there is a positive charge, equal to the nega-` tivecharge induced on the inside of the inner conductornear the body.However, initially no charge appears on the outer surface of the innerconductor 20. The induced charge moves with the charged body along theinner surface of conductor 2@ until the end of the inner conductor 29 isreached. During the passage of the charged body across the gap 25, thecharge is partially imaged on the end of the inner conductor 2B andpartially on the outer conductor 2B as shown in Figure 2. The passage ofthe charged body beyond the gap 25 into the conductor 2B causes theinduced charge all to appear on the inner surface of the conductor 2t asshown in Figure 3. The induced charge in transferring from the end ofthe inner conductor to the conductor 26 flows back over the outersurface of the inner conductor 29 and the inner surface of conductor 2i,thus constituting a current iiow in the quarter wave tank circuit. 1fcharged bodies are projected past the gap in proper phase and frequencyrelationship with respect to the resonant frequency of the tank circuit,the circuit may be made to oscillate vigorously merely by the passage ofthe charged bodies past the gap.

Figure 4 illustrates the conguration of the electric and magnetic fieldswithin the resonant space of the tank circuit when the latter isexcited. The solid lines 21 represent the electric eld distribution andthe circles 28 represent the magnetic lines of force. The dashed lines2! represent the equi-potential surfaces in the gap. Along the majorpart of the length of the tank circuit the direction of the electric eldis sublstantially radial. However, at the gap 25 the electric eld has anaxial component. The electric eld does not penetrate very far inside theopen end of the inner-conducting member 20 or inside the conductor 24,but is conilned eiectively to the space dened approximately by thelimiting equipotential lines 29 shown in the figures. The space insidethe inner conductor 20 and inside the conductor 24 is essentially eldfree, therefore no work will-be done on a charge moving inside the innerconductor 20 by the electric field until the charge reaches the gap 25.If the charge traverses the gap at the instant when the electric forceis in the direction from 20 to 24, the charge will be decelerated, itsenergy being given up to the tank circuit. A charge crossing the gapduring the opposite half cycle when the iield is reversed will beaccelerated and absorb energy from the circuit. If, however, the nurnberof charges traversing the gap during the rst half cycle is greater thanduring the second, the net effect will be that energy is supplied to thetank circuit.

Thus, the tank circuit may be excited by passing groups of electrons atthe proper frequency across the gap between the conductors 2li and 24.The motion of the electrons in the interior ofv the inner conductor 20has no effect on the current in the tank circuit. Also high frequencyelectromagnetic'ilelds which will be generated within the resonatingspace of the tank circuit penetrate but a short distance inside theconductor 2t and conductor 24 which act as a screen electrode so thatthe electrons will be inuenced circuit including electrodes 20 and 24'and also Y between the collector 32 and cathode 30. a stream ofelectrons from the cathode will flow toward the collector. If a highfrequency voltage is applied between the control grid and the cathode,the electron stream will be periodically modulated in intensity. Pulsesof electrons traversing the gap 25. will induce high freouencv currentsbetween the electrodes 20 and v24'. If the excitation frequency isadjusted to the resonant freouency of the tank circuit a high impedancewill exist across the gap-25 at this frequency. The induced currents,therefore, will produce a high radio frequency voltage across the gan25. The phase of this voltage at or near resonance lwill be such as todecelerate electrons traversing the gap during the half period ofmaximum intensity oi' the .electron current in the stream.

'I'he energy lost by the electrons is transformed by the tank circuitinto the energy oi' the electromagnetic iield within the resonatingspace between the inner and outer conductors and then may be conveyed to'the useful load by means o f a coupling loop such as, for example, 33extending through an aperture inthe outer tubular conductor El of thetank circuit.

'Ihe high yfrequency electromagnetic ileld existing in the resonantspace of the tank circuit penetrates only a short distance insidethetubular electrode 20 and inside the tubular screen electrode 24.Therefore, by positioning the control electrode 3| at a suitabledistance from the gap 25 the coupling between the input electrodes 30and 3| and the output electrodes 2|! and 24 can be reduced to anegligible value. The collector electrode is also placed at an adequatedistance from the gap to minimize coupling between it and the tankcircuit. This results in a reduction of the lossesv caused by theabsorption of radio frequency energy from the tank circuit by thecollector. Y

To minimize the transit time effect the electrodes 20 and 24' can beoperated at suitable high potentials with respect to the cathode. Theadjustment of these potentials is not critical because the functioningof the tube does not depend critically upon the electron transit time.'Ihis is because the electrons are effective in exciting the outputcircuit only during the short period of time that they pass through theileld extending through the gap 25. The current collecting electrode 32can be operated at amuch lower potentialthan the conductors 20 and 24'and in order to obtain a high efflciencyit is usually operated at apotential just suiflcient to collect all decelerated electrons. Toimprove the functioning of the device an electrostatic or magneticfocusing of the electron stream can be utilized to prevent electronsfrom impinging on the high potential electrodes 20 or 24'. .Thus theseelectrodes will not dissipate energy and all of the power generated inthe tube will be supplied by the low voltage collector power supply.

In Figure 6 is shown a tube in longitudinal section' and made accordingto my invention. The main body of the tube, which constitutes a quarterwave concentric line output tank circuit includes a pair of tubularcoaxial members or electrodes 35 and 36 separated axially by a gap 31and electrically connected to a concentric outer cylinder or tubularmember 38 by means of end plates 39 and 40. Mounted within the tubularmember 35 is an indirectely heated cathode 4|, the heater of which isnot shown, and a grid 42. These electrodes may be disc or rectangularshaped. Electrons supplied by the cathode 4| are projected axiallywithin the cylinders 35 and 36 to a collecting electrode 43 preferablyof carbon. The glass cup members 44 and 45 close the ends of the tubularmembers 35 and 36 to provide with the member 38 an envelope for theelectrodes, the cup-shaped member 44 being sealed to the tubular member35 and the cup-shaped member 45 being sealed to the electrode 36 whichwill be referred to as a screening electrode. The solenoid 46 may beprovided for focusing the electrons from the cathode 4| into a welldefined beam along the axis of the tubular electrodes 35 and 36. Thelelectrodes 4| and 42 are suitably supported by means of the conductors41 and 48. A parallel Wire transmission line is'attached to theseconductors. This line forms the input circuit which is tuned by thebridging member 49 provided with the by-passing condenser 50. A loop 5|serves to couple the input circuit to a driver. To permit the tankcircuit to be coupled to a load, an aperture 38' is provided in theouter tubularmember 38, surrounded by an extension or collar 38". Areentrant glass portion 53 sup- 'that these electrodes dissipate noenergy.v

assess? ported on and sealed to the extension 38" is extended throughthe aperture Il' in the outer tubular member it to permit the insertionof a coupling loop lll and to seal the tank circuit.

The source oi' voltage lid connected Ibetween the Y grid and' cathodeprovides o. proper bias on grid di, voltage source till beingprovidedfor applying to the tanh `circuit by means of conductor tt' avoltage higher than that applied to the collecting electrode by thepower supply til.

when a high potential de at B is applied between the cathode and theelectrodes lill endl@ and a voltage Emu at llt between the cathode andcollector G3 a stream of electrons from the cathode li focused by themagnetic eld of the solenoid 4l@ is projected toward the collector 68without imninsind on either electrode St or 536. Ii a radio frequencyvoltage is applied betwn control grid l and cathode di by exciting theinput circuit the electron stream will be periodically modulated inintensity. Pulses of electrons traversing the gap fil will induce radiofrequency currents' in the electrod 8d and 8f3. lli .the encitationfrequency is adjusted to the resonance frequency oi the output circuit35. 39 andllla high impedance will exist across Athe gap 3l at thisfrequency. Consequently, currents induced' in electrodes @El ond SG byelectron puls@ `evill produce a'high radio'ireqluency voltageecrm thegap 8l. The phase oi'this voltage at or near resonance will be such esto decelerate electrons passing during the half period oi maximumintensity oi electron current in the stream. The energy ci thedecelerated electrons is converted by the tank circuit into energy oithe electric and magnetic nelds in the resonant space between the inner85 and outer 88 cylinders and then transferred to the useful load by thecoucling loop B2.

The radio frequency nelds penetrate only a short distance inside thetubular electrode d5 and inside the screening electrode 38. a distanceel iectively less than their diameter so that by mn tloning the cathodedi; control electrode il and the `collector lil at suitable distancestrom the sap 3l, the couplins between the output tank circuit and theselast three mentioned electrodes can loe made practically negligible. Toreduce electron transit time hetweni the control grid dil and the gap,the electrodes t5 and 8S can he operated et suitable nich potentiele toincrease the speed oi the electrons past the gesp. Hop ever, to ohtmnedlilency, the collector electrode potentiel can he adjusted to a valuelust snmcient to collect lall decelerated electrons md usually has to heonly slightly higher than the edective com radio ireouen'cy voltagevcristinay across the gap. The adjustment o? the accelera ating'potential lds@ is not at all crlticel. lt is usually udine-ted m such avalue that the time oi electrons across the edectlve length o? the gap(anali-er than the diameter oi the elec trede Sli) is a Erection oi aperiod so that the lern in trensconductmce due to transit is With properand a sumcient locusing ideld is no current 'to electrodes 85 and 853 soThe correr is supplied only hy the collector 58.

F? is shown on in n the outp ctrodes and tenir are en tornai to tuteenvelope. 'ln this the inner tuloular menacer or electrode f5@ andocres".-

Si are joined and electricelly con were@ lo cuter @il ty o! conductingplates B3 and 54. These elements `form the concentricl line output tankcircuit.

The resonant frequency oi the tank circuit may be varied by means of theadjustable condenser plate 'I5 movable by insulated rod 'It' toward andfrom the electrodes and 8i to increase or de'- crease the capacitycoupling between these two electrodes. The edges of the electrodes 60Vand di are thickened and rounded as at te' and Il' to prevent excessiveradio frequency elds at the gap with a consequent dielectric loss in theglass envelope t@ housing the cathode and collector electrodes.Tominimize these losses the glass envelope may be provided with Ha shortsection near the gap made of low loss dielectric such as special glass,quartz or ceramic. To provide cooling for the tube and particularlyto-eiiect adequate cooling of Ythe glass envelope in the region ofmaximum-electric eld at the gap a special cooling arrangement can beprovided as shown by providing a reentrant portion t5 contacting theglass envelope and forming with the inner tubular members t@ and 6i ahollow tubular casing around the envelope into which air can be forcedthrough tubes t5' and tt", as indicated. The whole external concentricline tank circuit and the glass envelope can be separated at will.mvelope 556 which tits within the concentric tank circuit is providedwith an indirectly heated cathode 6l (heater not shown), control grid edand focusing electrode til, which can be maintained at either controlgrid potential or any suitable potential serving to concentrate theelectron stream at the start and making it possible to use considerablyweaker magnetic locusins delds from solenoids ld and lll withoutundesirable current absorption by the accelerating electrodes 'l0 l andli positioned between the cathcde and collector electrode l2 supportedfrom the press i8. The reason lor using the accelerating electrodes l0and li is to avoid the undesirable -edects ol charges on the glass walldue to bombardment hy stray electrons. The electrodes l@ end li arepositioned at a suitable distance from the gap between the electrodes BQand @i oi the output tenir circuit so that the radio ire quency deldsfrom the space between the tubular members GU and @l do not reach thorn,and thus electrodes l@ end li do not form a part of the output circuitand do not carry circulating currents. The electron stream from thecathode lll modulated py grid S0 focused by the electrode 69 traversesthe sap' between electrodes O@ and ci. is in the previous case a highradio lreduency voltage will ce developed across the gap and electronswill he decelerated in the aap and nnslly alter passing acceleratingelectrode ll will te collected hy means oi electrode il. Radio irenuencyenergy is transferred from the tenir circuit hy the coupling loop Gl' tothe load.

A persllel wire www., on line comprising tubular conductors lli and El@tuned by e conduct ing bridge Si iorni the input circuit. Conductors 6d'and El connected to the focusing electrode d@ and grid @il entendthrough tubular member l@ and are connected to the voltage sources 69"and 58' to provide the hissing voltages lor the locusing electrode Si)and the grid Gd. Thetuloular member 8O md the insulated conductor 'JQrwithin the tubular member iurnish the cathode heating n current fromthe source oi voltage supply 6l' and bers l and 8l having a diameterjust sufficiently large to permit slipping the concentric line unit overthe end of the envelope 66 having an outside diameter of 1%". The gapbetween the inner tubular member 80 and 8l was of the order of Theaccelerating electrode 'H with a width of t'fwas spaced 2" from theaccelerating electrode Il having a width of 1", the focusing electrodebeing spaced 115" from the edge of the accelerating electrode 10. Thecollecting electrode 'I2 has an outside diameter` of 2" and a depth of2". It is of course understood that these dimensions could be changed orvaried for different frequencles and. for different power outputs.

The tube was operated under the following con-.- ditlons: At a frequencyof 450 megacycles, power output of 110 watts was obtained, the drivingpower being about watts and the eillciency about 35%. The acceleratingvoltage applied to electrode 10 and 1I was of the order of 6000 voltsand the collector electrode Voltage of the order of 2000 volts. Thecollector current was approximately 150 milliamperes. l'I'he extremelylow loss in the accelerating electrodes 10 and 1I is shown by the factthat less than .1 milliampere was the current tol these electrodes. Thisperformance which is readily obtained with a tube made according to myinvention contrasts sharply with tubes and circuits of conventionaldesign when -an attempt is made to operate them at the higherfrequencies.

Thus in a tube made according to my invention electron transit timeeffects are minimized by utilizing electrons of high velocity. This isaccomplished without increasing dissipation and loss in eiliciency byseparating the functions of the output electrode and current collectingelectrode and by making use` of electron focusing. 'I'he output-inputcoupling is reduced to a negligible value by screening and separation ofthe Y electrodes and circuits. 'I'he high frequency losses due to highfrequency voltages are minimized by current carrying electrodes of largeperiphery.

` In addition to the above advantages high eilieiency results due tocollection of the electrons at low velocity and high power output isattained because the collector may be made Iof adequate size withoutinuencing the performance of the output circuit. A non-regenerativeampliication is made possible through the reduction of theyrmtput-inlrut coupling to a negligible value.

Other uses to `which my invention may be put are for example frequencymultiplication an generation of oscillations.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specic applicationfor which my invention may be employed, it will be apparent that myinvention is by no means limited to the exact forms illustrated or theuse indicated, but that many variations may J be made in the particularstructure used and the se for which it is employed Without depart-n ingfrom the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device including a cathode and grid forsupplying a modulated stream of electrons anda collecting electrode forreceiving said modulated stream of electrons, and a quarter waveconcentric line output tank circuit having a pair of coaxial tubularmembers axially spaced to provide a gap and surrounding the dischargepath between the cathode and anode whereby electrons from, the cathodeto the anode traverse the gap between said pair of coaxial tubularmembers, and accelerating means including a pair of electrodessurrounding the path of the beam between the cathode and the collectingelectrode.

2. An electron discharge device including an envelope containing acathode and grid for sup plying amodulated stream of electrons and anelectrode for collecting electrons in said stream, a tank`circuitsurrounding said envelope and including a pair of coaxial tubularmembers spaced axially to form a gap therebetween surrounding thedischarge path between the cathode and the collecting electrode, andelectromagnetic means surrounding said tubular members for focusing theelectrons from the cathode to the collecting electrode into awell-defined beam.

3. An electron discharge device including an` envelope containing acathode and grid for supplying a modulated stream of electrons and anelectrode for collecting electrons in said stream, an accelerating meanswithin said envelope and including a pair of electrodes surrounding thepath of the electrons between the cathode and collecting electrode, atank circuit surrounding said envelope and including a pair of coaxialtubular members spaced axially to form a gap therebetween surroundingthe discharge path between the cathode and the collecting electrode, andelectromagnetic means surrounding said coaxial tubular members forfocusing they electrons from the cathode to the collecting electrodeinto a well-defined beam, and a conductor bridging the gap andoverlapping but out of contact with the adjacent ends of the coaxialtubular members and movable transversely of the coaxial tubular membersto change the capacity coupling between said coaxial tubular members.

4. An electron discharge device including an envelope having a cathodeand grid for supplying a modulated stream of electrons and an electrodefor collecting electrons in said stream, and accelerating means withinsaid envelope and including la pair of electrodes surrounding the pathof the stream between the cathode and the co1- lecting electrode, a pairof coaxial tubular members spaced axially to form a gap therebetweensurrounding the discharge path between the cathode and the collectingelectrode, a conducting plate member secured to each of said coaxialtuburlar members intermediate the ends of the tubullas members andelectrically connected at their peripheries by a conducting cylindricalmember to form a tank circuit and a. conductor bridging the gap andoverlapping but out of contact 'with the adjacent ends of the coaxialtubular members electrode for collecting said electrons, a hollow tankcircuit surrounding said envelope and having a gap lying in a planetransverse to the stream of electrons and between the grid andcollecting electrode, said tank circuit being spaced from said envelopeto provide a passageway between the envelope and the tank circuit, andmeans for directing a cooling medium between theenvelope and the tankcircuit.

6. An electron discharge device including an envelope containing acathode and grid for supplying a modulated stream of electrons, and anelectrode for collecting the electrons in said stream, an elongatedhollow tank circuit surrounding said envelope and including a pair ofcoamal tubular members spaced axially to form a gap therebetweensurrounding the discharge path between the cathode and the collectingelectrode, said tubular members being spaced from said envelope toprovide a passageway between the envelope and the tubular members, andmeans for directing a cooling medium between the envelope and thetubular members into the interior of the tank circuit through said gap,said last means including extensions on opposite ends of said tankcircuit and enclosing a space around the envelope, said spacecommunicating with the space between the tank circuit and envelope andhaving inlets for introducing the cooling medium.

7. An electron discharge device including an envelope containing acathode and a grid for supplying a modul-ated stream of electrons, andan electrode for collecting the electrons in said stream, a hollow tankcircuit surrounding said envelope and including a pair of coaxialtubular members spaced axially to form a gap therebetween surroundingthe discharge path between the cathode and collecting electrode and aconacr ducting member surrounding said coaxial tubular Y members andsecured and electrically connected to each of said coaxial tubularmembers, said coaxial tubular members being spaced from the envelope toprovide an annular passageway between the envelope and the tubularmembers, inlet means for directing a cooling medium between the envelopeand the inner tubular mem- .bers through said gap into the interior oisaid tank circuit, said conducting member surrounding said tubularmembers being provided with an aperture through which the cooling mediumcan pass to the exterior of the tank circuit.

8. An electron discharge device including an envelope containing acathode and grid :for supplying a modulated stream of electrons and anelectrode ior collecting the electrons in said stream, acceleratingmeans within the envelope and including a pair of electrodes surroundingthe path'oi the electrons between the cathode and. the collectingelectrodes,- a twk circuit surrounding said envelope and including apair oi coaxial tubular members spaced axially toform e, gaptheretbetween surrounding the discharge path between the cathode and thecollecting electrede and .a conducting member surrounding said coamaltubular member and secured and elec2 tricallr connected to each of saidcoaxial tubular members, and electromagnetic means surround= theconducting member for io cusing electrons from the cathode to thecollecting electrode into a welldeiined beam.

9. hn electron discharge device including an envelope a cathode and gridfor supplying a modulated stream of electrons and an electrede forcollecting electrons in said stream and accelerating means within saidenvelope and in=1 iti cludin'g a pair of electrodes surrounding the pathof the beam between the cathode and the collecting electrode, a tankcircuit surrounding said envelope and including a pair oi coaxialtubular members spaced axially to form a gap therebetween surroundingthe discharge path between the cathode and the collecting electrode anda conducting plate member secured to each of said coaxial tubularmembers intermediate the ends of the tubular members andelectrically'connected at their peripheries by a, conducting cylindricalmember, and a conductor bridging the gap and overlapping but out ofcontact with the adjacent ends of the coaxial tubular members andmovable transversely of the coaxial members to change the capacitycoupling between said mem- :bers to vary the frequency at which the tankcircuit will osoillate, and electromagnetic means surrounding each ofthe coaxial tubular members. 10. An electron discharge device includinga cathode and grid for supplying a. modulated stream of electrons, and acollecting electrode for collecting electrons` in said stream, and ahollow tank circuit surrounding said stream of electrons and including apair of coaxial tubular members spaced axially to form a gaptherebetween'surrounding the discharge path between the cathode andcollecting electrode and a conducting plate member secured to each ofsaid coamal tubular members intermediate the ends of the tubular membersand a conducting member electrically connecting said plates at theirperipheries, and electromagnetic means surrounding said tubular membersfor focusing the electrons projected from the cathode to the collectingelectrode in a well-defined beam, said conducting member electricallyconnected to the peripheries oi the conducting plate members having anaperture and a reentrant extension of insulating material extendingwithin said aperture and sealingsaid tank circuit, and a conducting loopextending within the reentrant insulating extension for coupling theelectron discharge device to an output circuit.

11.. An electron discharge device having a cathode for Supplying astream or electrons and means for collecting said electrons, a hollowtank circuit having a passageway extending therethrough through whichthe electrons iromthe cathode pass to the collecting means, saidpassageway having a gap surrounding the discharge path between thecathpde and the collecting means, an insulating means closing one end ofthe passageway to provide with the hollow tank circuit an envelope forthe cathode, said hollow tank circuit having an aperture extendingthrough the outer surface thereof, and an insulating closure membersupported within said aperL ture and sealing said aperture in saidhollow tank circuit, and a conducting coupling member extending withinthe hollow tank circuit through said aperture.

l2. lin electron discharge device having a cathode ior supplying astream oi electrons and means ior collecting said electrons, a hollowtank circuit having a j.=assagewav extending therethrough through whichthe electrons from the cathode paas to the collecting means, said pas=sagewar having a gap surrounding the discharge path between the cathodeand the collecting means, an insulating means closing one end or thepassageway to provide with the hollow tank circuit an envelope for thecathode, said hollow tank circuit having an aperture extending throughthe outer surace thereoi and ons tension around said aperture, and aninsulating closure member supported by said extension and sealing saidaperture in said hollow tank circuit, and a conducting coupling memberextending through the extension within the hollow tank circuit.

13. An electron discharge device having a cathode and grid for supplyinga modulated stream of electrons and means for collecting said electrons,a hollow tank circuit having a passageway extending therethrough throughwhich the electrons from the cathode pass to the collecting means. saidpassageway having a gap surrounding the. discharge path between thecathode and the collecting electrode, and insulating means closing oneend of the passageway to provide with the hollow tank circuit anenvelope for the cathode and grid, said hollow tank circuit having anaperture extending through the outer surface thereof and an extensionaround said aperture and insulating material supported by said extensionand sealing said aperture in said tank circuit and a conducting couplingmember extending through the extension within the hollow tank circuit.

14. An electron discharge device having a tank circuit comprising ahollow body formed by a surface of revolution and having a resonantfrequency and 4having a passageway extending through said hollow body,said passageway having a gap extending entirely around said passagewayand in a piane transverse to said passageway, a cathode for supplyingelectrons axially of said passageway past said gap, and means forcollecting theelectrons after the passage of electrons'past said gap,insulating cup-shaped members closing the opposite ends of saidpassageway and providing with said hollow body an envelope for saidcathode and collecting electrode, the outer surface of said hollow bodybeing provided with an aperture and a reentrant extension oi' insulatingmaterial extending within said aperture and sealing said hollow body,and a conducting coupling member extending within the er'tmt insulatingextension and said hollow 15. An electron discharge device including ahollow output tank circuit having a pair of coaxial tubular membersspaced axially to forma gapand a conducting member surrounding saidtubular members and conductively' secured to said coaxial tubularmembers, a cathode and grid positioned adjacent one end of one of saidcoaxial tubular members for supplying a modulated stream pf electronsaxially of said coaxial tubular members across said gap and a collectingelectrode adjacent an end of the other tubular member :for receiving theelectrons from the cathode after passage across said gap and cupshapedinsulating members closing the opposite ends of the coaxial tubularmembers to form with said hollow output tank circuit an envelope forsaid cathode, grid and collecting electrode, and a reentrant extensionof insulating material extending within said aperture and said hollowoutput tank circuit and sealing said tank circuit, and conductingcoupling means extending within the reentrant insulating extension.

16. An electron discharge device having a cathode for supplying a streamof electrons and means for collecting said electrons, a hollow tankcircuit having a passageway extending therethrough through which theelectrons from the cathode passto the collecting means, said passagewayhaving a gap surrounding the discharge path between the cathode and thecollecting means, means closing one end of the passageway to providewith the hollow tank circuit an envelope for the cathode, said hollowtank circuit having an aperture extending through the outer surfacethereof, and a cup-shaped insulating closure member extending withinsaid aperture and sealing said aperture in said hollow tank circuit, anda conducting coupling member withinthe hollow tank circuit extendingthrough saidiaperture.

17. An electron discharge device having a cathode for supplying a streamof electrons and means for collecting said electrons, a hollow tankcircuit having a passageway ,extending therethrough through which theelectrons from the cathode pass to the collecting means, said passagewayhaving a gap surrounding the discharge path between the cathode and thecollecting means, insulating means closing one end of the passageway toprovide with the hollow tank circuit an envelope for the cathode, saidhollow tank circuit having an aperture extending through the outersurface thereof, and a reentrant insulating closure member extendingwithin said aperture and sealing said aperture to said hollow tankcircuit, and a, conducting coupling member within the hollow tankcircuit extending through said aperture.

18. An electron discharge device having a cathode and grid for supplyinga modulated stream of electrons and an electrode for co1- lecting saidelectrons, a hollow tank circuit surrounding said stream of electronsand having a gap lying in a plane transverse to the stream of electronsand between the grid and collecting electrode, and a pair ofaccelerating and screening electrodes positioned between the grid andthe collector electrode,l one oi' the accelerating and screeningelectrodes being positioned on each side oi said gap.

` ANDREW V. HAEFF.

